Career
He started target shooting in 2002 and his first international competition was Oceania 2002, where he competed against other SH2 shooters. Johnson ended up with a fourth placing. However, at the 2004 Summer Paralympics in the SH2 Standing Air event, Johnson shot a perfect 600 out of 600 points world record round in the preliminaries and then equalled the world record for a gold medal in the finals with 704.3.
Later that year, Johnson represented his country in the 2008 Summer Paralympics in Beijing.
Johnson secured a bronze medal in the Mixed R4-10 m air rifle standing SH2 with a score of 701.2 after a shoot-off with South Korean shooter Ho-Gyoung You. 2009 started well with Johnson building towards London 2012 competing again at the Jikji Cup in South of Korea now called The Open Asian Shooting Championships.